JP5556582B2 - Waste heat recovery system - Google Patents

Description

  The present invention relates to an exhaust heat recovery system for an exhaust heat recovery unit that recovers heat of engine exhaust via a refrigerant.

  An exhaust heat recovery device that recovers engine exhaust heat (hereinafter referred to as exhaust heat) is provided in the cooling water system of an automobile engine, and this exhaust heat is used for promoting warm-up of the engine, heating the passenger compartment, and the like. A technique is known (see, for example, Patent Document 1). The exhaust heat recovery device is disposed in the middle of the exhaust pipe of the engine and includes a flow path through which cooling water flows. When the engine cooling water flows through the exhaust heat recovery unit, the engine cooling water recovers the exhaust heat by exchanging heat with the engine exhaust.

  Here, for example, FIG. 5 shows an example of an exhaust heat recovery system for completing the warm-up operation of the engine at an early stage when the engine is cold-started. As shown in FIG. 5, an exhaust heat recovery device 2, a radiator 4, an oil warmer 7, and a water pump 8 are provided on the cooling water flow path 10 of the engine 1. In addition, a cooling switching valve 5 for switching whether or not to flow the cooling water to the radiator 4 is provided at the junction of the cooling water flow path 10, and the exhaust heat recovery switching valve 3 ′ for switching whether or not to perform exhaust heat recovery. Is provided at the junction of the exhaust pipe 20.

The cooling switching valve 5 changes the flow path 10 through which the cooling water flows by opening and closing according to the temperature of the cooling water. Specifically, the cooling switching valve 5 is closed when the temperature of the cooling water is relatively low (for example, when the engine 1 is cold-started) so that the cooling water does not flow to the radiator 4. The circulation of the cooling water between 1 and the radiator 4 is stopped. As a result, the engine 1 is quickly warmed up. When the temperature of the cooling water reaches the valve opening temperature T ₀ of the cooling switching valve 5, the cooling switching valve 5 is opened and the cooling water is circulated between the engine 1 and the radiator 4. Thereby, since the cooling water cooled with the radiator 4 is supplied to the engine 1, even if the engine 1 after warming-up becomes high temperature, it cools to appropriate temperature.

The exhaust heat recovery switching valve 3 ′ is provided on the upstream side of the cooling water of the exhaust heat recovery device 2, and changes the route of the exhaust pipe 20 through which the exhaust flows according to the temperature of the cooling water flowing into the exhaust heat recovery device 2. To do. This will be described with reference to FIG. FIG. 6 is a diagram illustrating switching of the exhaust heat recovery switching valve 3 ′ with respect to the temperature of the cooling water. As shown in FIG. 6, the exhaust heat recovery switching valve 3 ′ is opened when the temperature of the cooling water is relatively low, and the exhaust heat recovery is performed by switching the path so that the exhaust flows to the exhaust heat recovery device 2. I do. Thereby, cooling water is heated and warming up of the engine 1 is further promoted. When the temperature of the cooling water reaches the closing temperature T ₁ ′ of the exhaust heat recovery switching valve 3 ′, the exhaust heat recovery switching valve 3 ′ is closed so that the exhaust gas does not flow to the exhaust heat recovery device 2. Switch the path and stop the exhaust heat recovery. This prevents the cooling water from being heated more than necessary.

Note that the closing temperature T ₁ ′ of the exhaust heat recovery switching valve 3 ′ is set lower than the opening temperature T ₀ of the cooling switching valve 5, and before the cooling water is started to be cooled by the radiator 4. The exhaust heat recovery by the heat recovery device 2 is stopped. Further, after exhaust heat recovery is stopped, if the temperature of the cooling water decreases to the opening temperature T _{2 of the} exhaust heat recovery switching valve 3 ′ due to the operating state of the engine 1 or the climate, the exhaust heat recovery is performed. The switching valve 3 'is opened again to recover the exhaust heat.

JP 2010-19216 A

  However, in the case of the exhaust heat recovery system as described above, the exhaust heat recovery switching valve 3 ′ for switching whether or not to perform exhaust heat recovery is provided on the upstream side of the cooling water of the exhaust heat recovery device 2. The heat recovery switching valve 3 ′ opens and closes according to the temperature of the cooling water before passing through the exhaust heat recovery device 2. Therefore, even if the temperature of the cooling water is raised more than necessary and exceeds the allowable temperature of the cooling water immediately downstream of the exhaust heat recovery unit 2, it cannot be detected.

Further, in the exhaust heat recovery system as described above, for example, as shown in FIG. 5, the engine is used by using the cooling water heated through the exhaust heat recovery device 2 on the downstream side of the exhaust heat recovery device 2. An oil warmer 7 that heats oil or transmission oil may be provided.
Engine oil and transmission oil are high in viscosity at low temperatures and have large friction, which is a cause of deterioration in fuel consumption. The oil warmer 7 heats these oils when the oil temperature of the engine oil or transmission oil is low, such as during cold start, and thereby raises the temperature early, thereby reducing friction loss and improving fuel efficiency. The purpose is that.

However, while the cooling water is heated by the engine 1 and the exhaust heat recovery device 2 and is easily heated due to the system configuration, the engine oil and the transmission oil are passed through the heated cooling water. Since it was heated, the temperature was raised slowly compared to the cooling water (the temperature rise was gradual), and it took time to be sufficiently warmed.
Therefore, if the closing temperature T ₁ ′ of the exhaust heat recovery switching valve 3 ′ is set lower than the opening temperature T ₀ of the cooling switching valve 5 as in the above-described exhaust heat recovery system, the oil warmer 7 The exhaust heat recovery may be stopped before the temperature rise of the oil is completed. In other words, there are cases where the oils are not sufficiently heated even when the engine is warmed up.

This case has been devised in view of such problems, and the heating time of oils in the oil warmer is ensured by adequately controlling the temperature of the cooling water and ensuring sufficient exhaust heat recovery time by the exhaust heat recovery device. One of the objectives is to provide an exhaust heat recovery system that can secure sufficient energy consumption.
The present invention is not limited to this purpose, and is a function and effect derived from each configuration shown in the embodiments for carrying out the invention described later, and other effects of the present invention are to obtain a function and effect that cannot be obtained by conventional techniques. Can be positioned.

(1) In the exhaust heat recovery system disclosed herein, a cooling water flow path of an engine mounted on a vehicle is configured as a parallel flow path branched into a first circulation flow path and a second circulation flow path . Cooling water flows through the first circulation flow path and the second circulation flow path, and heat is exchanged between the cooling water and the engine exhaust in the first circulation flow path. an exhaust heat recovery unit for heating water, is provided in the cooling water downstream of the exhaust heat recovery unit, and an oil warmer for heating the oil is provided by performing said cooling water heat exchanger, the second circulation The flow path is an exhaust heat recovery system that is further branched into a cooling flow path in which a radiator for cooling the cooling water is interposed and a bypass flow path that bypasses the cooling flow path . Immediately after passing through the exhaust heat recovery device and the inflow state to the exhaust heat recovery device Depending on the temperature of the coolant, a first switching valve to shut off the flow to the exhaust heat recovery unit of the exhaust temperature in the second circulation channel of the cooling water passing through the engine is in a predetermined A second switching valve that shuts off the inflow of the cooling water to the radiator when the valve opening temperature (T ₀ ) is lower.
Further, the temperature of the cooling water when the first switching valve flows into the exhaust heat recovery device and immediately after passing through the exhaust heat recovery device is higher than the valve opening temperature (T ₀ ). When the temperature is higher than the first temperature (T ₁ ) set higher than the allowable temperature (T _MAX ) of the cooling water, the flow of the exhaust into the exhaust heat recovery device is blocked.

(2) The temperature of the cooling water when the first switching valve shuts off the inflow of the exhaust gas to the exhaust heat recovery device and immediately after passing through the exhaust heat recovery device is the valve opening temperature (T ₀ ). When the temperature is lower than the lower second temperature (T ₂ ), the exhaust gas is preferably allowed to flow into the exhaust heat recovery device.
(3) A cooling fan operating temperature that further includes a cooling fan that cools the radiator, and wherein the first temperature (T ₁ ) is a temperature in the cooling channel of the cooling water at which the operation of the cooling fan is started. The temperature is preferably lower than (T _FAN ).

(4) comprising a front Symbol exhaust pipe exhaust flows, the exhaust heat recovery unit and the first switching valve are both being disposed in the first circulation channel and the upper exhaust pipe, the first switching valve provided in the cooling water downstream of the exhaust heat recovery unit, before Symbol second switching valve, which is preferably disposed before Symbol second circulation channel.

According to the disclosed exhaust heat recovery system, the temperature of the cooling water immediately after passing through the exhaust heat recovery device is higher than the opening temperature (T ₀ ) of the second switching valve that blocks the cooling water from flowing into the radiator. Since the inflow of exhaust gas to the exhaust heat recovery unit is cut off when the temperature exceeds one temperature (T ₁ ), the cooling immediately after passing through the exhaust heat recovery unit even after the cooling water has flowed into the radiator The exhaust heat recovery can be continued until the water temperature becomes equal to or higher than the first temperature (T ₁ ).

In other words, can be continued for a while waste heat recovery from the end of warm-up of the engine, it can ensure a long inflow time to exhaust heat recovery device exhaust than the conventional. Therefore, since the cooling water having a temperature higher than the valve opening temperature (T ₀ ) can be supplied to the oil warmer provided on the downstream side of the cooling water of the exhaust heat recovery device, the temperature of the oil can be raised more quickly. it can. Thereby, the friction loss caused by the low temperature and high viscosity of the oils can be reduced, and the fuel consumption can be improved.

Further, the first temperature (T ₁ ) at which the inflow of exhaust gas to the exhaust heat recovery device is controlled according to the temperature of the cooling water immediately after passing through the exhaust heat recovery device and the first switching valve is shut off. Since the temperature is set lower than the allowable temperature (T _MAX ) of the cooling water, the temperature of the cooling water can be appropriately controlled without excessively increasing the temperature of the cooling water by the exhaust heat recovery device. For this reason, even if it sets so that the inflow time of exhaust_gas | exhaustion to an exhaust heat recovery device may become long, it can suppress reliably that the temperature of a cooling water exceeds allowable temperature ( _TMAX ).

In addition, when the first switching valve shuts off the inflow of exhaust gas to the exhaust heat recovery device and the temperature of the cooling water immediately after passing through the exhaust heat recovery device is higher than the opening temperature (T ₀ ) of the second switching valve. Only when the temperature of the cooling water has decreased too much due to a decrease in the outside air temperature or an increase in heating requirements by allowing the exhaust gas to flow into the exhaust heat recovery unit when the temperature is lower than the low second temperature (T ₂ ). Since the exhaust heat recovery is resumed, unnecessary exhaust heat recovery after completion of warm-up can be suppressed.

Further, when the first temperature (T ₁ ) is set lower than the operating temperature (T _FAN ) of the cooling fan, before the cooling water is raised to the operating temperature of the cooling fan, the first switching valve Since the route of the exhaust pipe can be switched to a route that does not perform exhaust heat recovery, it is possible to prevent the operating rate of the cooling fan from increasing.

1 is an overall schematic configuration diagram of an exhaust heat recovery system according to an embodiment. It is a figure which shows the opening / closing operation | movement with respect to the cooling water temperature of the exhaust heat recovery switching valve in the exhaust heat recovery system concerning one Embodiment. It is a figure which shows the temperature change of a cooling water when the exhaust heat recovery system concerning one Embodiment is implemented. It is a figure explaining the effect of the exhaust heat recovery system concerning one embodiment. It is a whole schematic block diagram of the waste heat recovery system for demonstrating the conventional subject. It is a figure which shows the opening / closing operation | movement with respect to the cooling water temperature of the exhaust heat recovery switching valve in the exhaust heat recovery system for demonstrating the conventional subject.

[1. Constitution]
Hereinafter, embodiments will be described with reference to the drawings. Note that the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not explicitly described in the following embodiment.
The exhaust heat recovery system according to the present embodiment is not only when the engine is started, but when a sufficient time has passed since the engine was stopped and the engine is restarted in a state where the temperature of the cooling water is sufficiently low. Also, when idling is performed by waiting for traffic lights or waiting in areas where the temperature is particularly low in winter, the temperature of the cooling water is low, and the temperature of the cooling water is raised quickly by exhaust heat recovery, so that the engine warms up. It is possible to apply it when it is desired to complete the process early. Here, an example in which the exhaust heat recovery system is applied at the time of cold start of the engine will be described. Moreover, about the apparatus corresponding to what was demonstrated by background art, the code | symbol same as background art is attached | subjected.

  As shown in FIG. 1, an exhaust heat recovery device 2, an exhaust heat recovery switching valve (first switching valve) 3, a radiator 4, a cooling switching valve (second switching valve) are disposed on a cooling water flow path 10 of the engine 1. 5) An oil warmer 7 and a water pump 8 are provided. The exhaust heat recovery device 2 is a device that heats the cooling water by exchanging heat between the cooling water of the engine 1 and the exhaust of the engine 1, and the radiator 4 is a device that cools the cooling water of the engine 1. is there.

  Cooling water is supplied to the engine 1 by a water pump 8 using the engine 1 as a drive source. This cooling water passes through a flow path in a cylinder block and a cylinder head (not shown), circulates through the flow path 10, and returns to the water pump 8. The flow path 10 is branched into a first circulation flow path 11 and a second circulation flow path 12 at a branch point 15, and the first circulation flow path 11 and the second circulation flow path 12 are configured as parallel flow paths. Yes. Further, the second circulation flow path 12 further branches into a cooling flow path 12a and a bypass flow path 12b at a branch point 16, and these are also configured as parallel flow paths.

  On the 1st circulation channel 11, the exhaust heat recovery device 2, the exhaust heat recovery switching valve 3, and the oil warmer 7 are provided in this order from the cooling water upstream side. The cooling water circulated through the first circulation channel 11 merges with the second circulation channel 12 at the junction 17 and returns to the suction side of the water pump 8. Moreover, the radiator 4 is interposed on the cooling flow path 12a of the second circulation flow path 12, and nothing is provided on the bypass flow path 12b. The cooling flow path 12a merges with the bypass flow path 12b at the merge point 18 on the downstream side of the radiator 4, and further merges with the first circulation flow path 11 at the merge point 17 on the downstream side. A cooling switching valve 5 is interposed at the junction 18 of the second circulation channel 12.

  The exhaust heat recovery device 2 is interposed on the first circulation channel 11 and the exhaust pipe 20 of the engine 1. That is, the first circulation flow path 11 and the exhaust pipe 20 are introduced into the exhaust heat recovery device 2. When the exhaust of the engine 1 passes through the exhaust heat pipe 2 through the exhaust pipe 20, the exhaust heat recovery device 2 is connected to the cooling water flowing through the exhaust heat recovery device 2 through the first circulation passage 11. Heat is exchanged between them, and the exhaust heat is recovered with cooling water. That is, the cooling water is heated by exhaust.

  The exhaust pipe 20 bypasses the exhaust heat recovery unit 2 at a branch point 21 on the exhaust upstream side of the exhaust heat recovery unit 2 and a path that passes through the exhaust heat recovery unit 2 (hereinafter referred to as an exhaust heat recovery path) 20a. It is branched into a route (hereinafter referred to as a bypass route) 20b. The exhaust heat recovery switching valve 3 is interposed on the branch point 21 of the exhaust pipe 20. The exhaust heat recovery path 20a and the bypass path 20b merge on the exhaust downstream side of the exhaust heat recovery unit 2.

The exhaust heat recovery switching valve 3 is connected to the exhaust heat recovery unit 2 in accordance with the inflow state of the exhaust gas from the engine 1 to the exhaust heat recovery unit 2 and the temperature of the cooling water immediately after passing through the exhaust heat recovery unit 2. Is a valve that switches the path through which the exhaust gas flows to the exhaust heat recovery path 20a and the bypass path 20b, and is configured as an open / close valve here.
The exhaust heat recovery switching valve 3 opens the exhaust heat recovery path 20a when the valve is opened, and closes the bypass path 20b so that the exhaust gas flows through the exhaust heat recovery path 20a and flows into the exhaust heat recovery unit 2. . On the other hand, the exhaust heat recovery switching valve 3 opens the bypass path 20b when the valve is closed and closes the exhaust heat recovery path 20a so that the exhaust flows through the bypass path 20b and flows into the exhaust heat recovery unit 2. Shut off. That is, when the exhaust heat recovery switching valve 3 is opened, the exhaust heat recovery is performed by the exhaust heat recovery device 2, and when the exhaust heat recovery switching valve 3 is closed, the exhaust heat recovery is stopped. Here, the temperature of the cooling water is acquired by a temperature sensor (not shown) provided as a part of the configuration of the exhaust heat recovery device switching valve 3.

As shown in FIG. 2, the exhaust heat recovery switching valve 3 is opened when the engine 1 is cold started because the temperature of the cooling water is relatively low, and exhaust gas is circulated only through the exhaust heat recovery path 20a. Exhaust gas is allowed to flow into the heat recovery unit 2. At this time, when the temperature of the cooling water immediately after passing through the exhaust heat recovery unit 2 reaches the valve closing temperature (first temperature) T ₁ of the exhaust heat recovery switching valve 3, the exhaust heat recovery switching valve 3 is closed. Then, the exhaust gas is circulated through the bypass path 20b to block the inflow of the exhaust gas to the exhaust heat recovery unit 2, and the exhaust heat recovery is stopped. The valve closing temperature T ₁ of the exhaust heat recovery switching valve 3 is set to be lower than the allowable cooling water temperature T _{MAX and} higher than the valve opening temperature (valve opening temperature) T ₀ of the cooling switching valve 5 described later. The valve closing temperature T ₁ is preferably set lower than a cooling fan operating temperature T _FAN described later.

Further, the exhaust heat recovery switching valve 3 is configured such that the temperature of the cooling water immediately after passing through the exhaust heat recovery device 2 is opened when the exhaust flow into the exhaust heat recovery device 2 is blocked. When the temperature becomes lower than the valve opening temperature (second temperature) T ₂ set lower than the temperature T ₀ , the exhaust gas is caused to flow into the exhaust heat recovery unit 2. That is, the temperature of the cooling water that has passed through the exhaust heat recovery device 2 rises above the valve closing temperature T ₁ , the exhaust heat recovery switching valve 3 is closed once, and then the temperature of the cooling water decreases and the valve opening temperature T _{When 2} is reached, the exhaust heat recovery switching valve 3 is opened to resume exhaust heat recovery.

  The oil warmer 7 is provided on the downstream side of the cooling water of the exhaust heat recovery device 2, and performs heat exchange with the cooling water that has been heated through the exhaust heat recovery device 2, thereby generating engine oil or Oils such as transmission oil are quickly heated. Here, the oil warmer 7 has an engine oil warmer and a transmission warmer (not shown). These may be arranged in parallel, or may be arranged in series with one of them upstream. The oil warmer 7 may be only one of the engine oil warmer and the transmission oil warmer.

  The radiator 4 is a radiator that radiates the heat of the engine 1 collected by the cooling water, and cools the cooling water of the engine 1. When the temperature of the cooling water from which the heat of the engine 1 is recovered is not so high, the radiator 4 cools the cooling water with the traveling wind. In addition, when the temperature of the cooling water becomes high, cooling of the cooling water cannot be satisfied with the traveling air alone, and therefore the electric cooling fan 6 provided in the vicinity of the radiator 4 is operated. The cooling fan 6 is rotationally driven by receiving power supply from a battery (not shown), and the rotation forms an air flow toward the radiator 4. Thereby, the heat dissipation effect of the radiator 4 is enhanced, and cooling of the cooling water in the radiator 4 is promoted.

The temperature of the cooling water at which the cooling fan 6 starts to operate (hereinafter referred to as the cooling fan operating temperature T _FAN ) is set to be lower than the allowable temperature T _MAX of the cooling water. Therefore, the temperature is set to a relatively high temperature so that the cooling fan 6 is not inadvertently operated. Further, when the temperature sensor 13 detects that the temperature of the cooling water has reached the cooling fan operating temperature T _FAN , the cooling fan 6 is driven and controlled by the controller 9 described later. As shown in FIG. 1, the temperature sensor 13 may be provided on the flow path 10 on the upstream side of the branch point 15, and the upstream position of the exhaust heat recovery device 2 on the first circulation flow path 11 or It may be provided upstream of the branch point 16 on the second circulation channel 12.

  A controller (Engine (electronic) Control Unit, hereinafter referred to as ECU) 9 is a CPU that executes various arithmetic processes related to engine control, exhaust purification control, and the like, and a ROM and CPU that store programs and data necessary for the control. The RAM includes a RAM that temporarily stores the calculation results and the like, an input / output port for inputting / outputting signals to / from the outside, and the like. Detection results from various sensors such as a temperature sensor 13 and an engine speed sensor (not shown) are transmitted to the controller 9, and the controller 9 controls driving of the devices based on these detection results.

  The cooling switching valve 5 opens and closes according to the temperature of the cooling water that has passed through the engine 1, thereby blocking the inflow of the cooling water into the radiator 4, that is, the cooling flow through the flow path of the cooling water. It is a valve for switching between the passage 12a and the bypass passage 12b, and is provided at a junction 18 between the cooling passage 12a and the bypass passage 12b downstream of the radiator 4. Further, the cooling switching valve 5 here is constituted by a general thermostat and mechanically switches the flow path.

  The cooling switching valve 5 opens the cooling flow path 12a when the valve is opened and closes the bypass flow path 12b, thereby allowing the cooling water to flow through the cooling flow path 12a and flowing into the radiator 4. On the other hand, the cooling switching valve 5 opens the bypass flow path 12b when the valve is closed and closes the cooling flow path 12a, thereby allowing the cooling water to flow through the bypass flow path 12b and blocking the flow of the cooling water to the radiator 4. To do.

The cooling switching valve 5 is closed because the temperature of the cooling water is relatively low when the engine 1 is cold started, and the cooling water is circulated through the bypass flow path 12b, so that the cooling water between the engine 1 and the radiator 4 is closed. Stop circulation. Further, when the temperature of the cooling water flowing through the cooling switching valve 5 reaches the valve opening temperature T ₀ of the cooling switching valve 5, the valve opens, and the cooling water flows through the cooling flow path 12 a and flows into the radiator 4. The cooling water is circulated between the engine 1 and the radiator 4. The valve opening temperature T ₀ of the cooling switching valve 5 is set to a temperature (for example, about 80 ° C.) at which the engine 1 is maintained at an appropriate temperature. Further, the cooling switching valve 5 closes again when the temperature of the raised cooling water decreases again and reaches a temperature at which cooling of the cooling water by the radiator 4 is unnecessary, and the cooling water between the engine 1 and the radiator 4 is closed. Stop circulation.

Here, the cooling switching valve 5 is provided at the junction 18 downstream of the radiator 4, but may be provided at the branch point 16 upstream of the radiator 4.
[2. Action]
Since the exhaust heat recovery system according to the present embodiment is configured as described above, the exhaust heat recovery by the exhaust heat recovery device 2 is performed as follows.

As shown in FIG. 3, the engine 1 starts to be started at time A _S. The temperature of the cooling water at this time is a relatively low temperature T _S. When it is detected that the cooling water is at the temperature T _S , the exhaust heat recovery switching valve 3 is opened as shown in FIG. 2 to allow the exhaust gas to flow through the exhaust heat recovery path 20a and to the exhaust heat recovery unit 2 Exhaust heat recovery is performed by exchanging heat with the cooling water flowing through the first circulation channel 11 by flowing in the exhaust. Thereby, the temperature of the cooling water flowing through the first circulation flow path 11 is raised, and the oil warmer 7 provided on the downstream side of the exhaust heat recovery device 2 is used to raise the oils using the raised cooling water. The temperature is raised.

The cooling switch valve 5, the temperature of the cold start A _S in the cooling water of the engine 1, and closed because it is cold T _S than the valve opening temperature T _0, the cooling water in the bypass passage 12b The coolant is circulated to block the cooling water from flowing into the radiator 4 and the circulation of the cooling water between the engine 1 and the radiator 4 is stopped. As a result, the cooling water is not cooled by the radiator 4, and the temperature of the cooling water gradually rises and the warming up of the engine 1 is not hindered.

When the engine 1 is started and warmed up, the temperature of the cooling water gradually increases. At time A ₀ , the temperature of the cooling water reaches the valve opening temperature T ₀ of the cooling switching valve 5. At this time, the cooling switching valve 5 is opened, the cooling water is circulated through the cooling flow path 12a, the cooling water is caused to flow into the radiator 4, and the cooling water is circulated between the engine 1 and the radiator 4, In the radiator 4, cooling of the cooling water is started. However, at this time, as shown in FIG. 2, the exhaust heat recovery switching valve 3 is in the open state, and the cooling water of the engine 1 is cooled on the one hand by the radiator 4 and on the other hand the temperature is raised by the exhaust heat recovery device 2. Will be in a state.

  At this time, the radiator 4 is only cooled by the traveling wind, and the cooling fan 6 is not yet operated. Therefore, while the cooling water is cooled by the radiator 4, the temperature continues to rise due to heat exchange between the exhaust gas and the cooling water by the exhaust heat recovery device 2 and the heat of the engine 1. During this time, the oil warmer 7 continues to raise the temperature of oils such as engine oil and transmission oil.

When the temperature of the cooling water reaches the closing temperature T ₁ of the exhaust heat recovery switching valve 3 in this state where the exhaust gas flows into the exhaust heat recovery device 2, the exhaust heat recovery switching valve 3 is closed and the bypass path Exhaust gas is circulated through 20b to block the inflow of exhaust gas to the exhaust heat recovery unit 2, and the exhaust heat recovery is stopped. Since the valve closing temperature T ₁ is set lower than the allowable temperature T _MAX of the cooling water, the temperature of the cooling water at the time of passing through the exhaust heat recovery device 2 is equal to the allowable temperature T _MAX of the cooling water. Never exceed. Thereby, the overheating by the raise of the cooling water temperature in the exhaust heat recovery device 2 is prevented.

At time A ₁ when the exhaust heat recovery is stopped, as shown by a solid line in FIG. 3, the temperature of the cooling water gradually decreases and becomes substantially constant at the valve opening temperature T ₀ of the radiator 4 at time A ₂ . The water temperature is kept at an appropriate temperature. Then, as shown by a two-dot chain line in FIG. 3, the temperature of the cooling water decreases below the valve opening temperature T _{0 of the} radiator 4 due to some factor such as a decrease in the outside air temperature or an increase in the heating requirement, and the exhaust heat recovery switching is performed. When the valve opening temperature T ₂ of the valve 3 is reached, the exhaust heat recovery switching valve 3 is opened again and the exhaust heat recovery is resumed. After the warm-up is completed by setting the valve opening temperature T _{2 of} the exhaust heat recovery switching valve 3 (the temperature at which exhaust heat recovery is resumed) to a temperature sufficiently lower than the valve opening temperature T ₀ of the radiator 4. The unnecessary exhaust heat recovery is not performed.

[3. effect]
Next, the effect obtained by applying this exhaust heat recovery system will be described with reference to FIG. FIG. 4 schematically shows a temperature change during cold start of the engine 1 when the exhaust heat recovery system according to the present embodiment is applied and when the conventional exhaust heat recovery system described in the background art is applied. FIG. In FIG. 4, the solid line indicates the present exhaust heat recovery system, and the alternate long and short dash line indicates the conventional exhaust heat recovery system.

As shown in FIG. 1, when an oil warmer 7 is provided on the downstream side of the cooling water of the exhaust heat recovery unit 2, the oil warmer 7 is heated to pass through the exhaust heat recovery unit 2 to heat oils. Since cooling water is used, the temperature of these oils rises more slowly than that of cooling water, and the oil temperature rise gradient is smaller than that of cooling water, as shown in FIG. Further, in the conventional exhaust heat recovery system, since the valve closing temperature T ₁ ′ of the exhaust heat recovery switching valve 3 ′ is set lower than the valve opening temperature T ₀ of the cooling switching valve 5, the exhaust heat recovery is cooled. This was only performed until the temperature of the water reached T ₁ ′, and the exhaust heat recovery was completed before the oil was sufficiently heated.

On the other hand, in this exhaust heat recovery system, the temperature of the cooling water immediately after passing through the exhaust heat recovery device 2 becomes equal to or higher than the first temperature T ₁ higher than the valve opening temperature T ₀ of the cooling switching valve 5. In addition, since the inflow of exhaust gas to the exhaust heat recovery unit 2 is blocked, the exhaust heat recovery can be continued even when cooling of the cooling water by the radiator 4 is started, and the exhaust heat recovery time is ensured for a long time. be able to. Along with this, the oil warmer 7 can be supplied with cooling water heated to a temperature T ₁ higher than the valve opening temperature T ₀ for a long time, so that oils such as engine oil and transmission oil are also sufficient. Can be heated. As a result, the friction loss caused by the low temperature and high viscosity of the oils can be reduced, and the fuel efficiency can be improved.

Further, the closing temperature at which the exhaust flow into the exhaust heat recovery device 2 is controlled according to the temperature of the cooling water immediately after passing through the exhaust heat recovery device 2 and the exhaust heat recovery switching valve 3 is shut off. Since T ₁ is set lower than the allowable temperature T _MAX of the cooling water, the temperature of the cooling water is appropriately controlled without the temperature of the cooling water being raised above the allowable temperature T _MAX by the exhaust heat recovery device 2. can do. Thereby, even if it sets so that the inflow time of the exhaust_gas | exhaustion to the exhaust heat recovery device 2 may become long, it can suppress reliably that the temperature of a cooling water exceeds allowable temperature _TMAX .

In other words, this exhaust heat recovery system is not simply an extension of the exhaust heat recovery time, but also the exhaust heat recovery time while appropriately controlling the temperature of the cooling water so that the temperature of the cooling water does not rise excessively. It is considered that the heating time of oils in the oil warmer can be sufficiently secured and the fuel consumption can be improved.
In addition, when the inflow of the exhaust gas to the exhaust heat recovery device 2 is interrupted and the temperature of the cooling water immediately after passing through the exhaust heat recovery device 2 is lower than the valve opening temperature T ₀ of the cooling switching valve 5, the valve opening temperature T _2. The exhaust heat recovery switching valve 3 causes the exhaust gas to flow into the exhaust heat recovery device 2 when the temperature is lower than that, and the exhaust heat is exhausted only when the temperature of the cooling water is excessively decreased due to a decrease in the outside air temperature or an increase in heating requirements. Since recovery is resumed, unnecessary exhaust heat recovery after completion of warm-up can be suppressed.

Further, if the valve closing temperature T ₁ of the exhaust heat recovery switching valve 3 that are configured lower than the cooling fan operating temperature T _FAN, before the cooling water is heated to a temperature T _FAN cooling fan 6 is running, Since the exhaust heat recovery switching valve 3 switches the path of the exhaust pipe 20 to the bypass path 20b, the exhaust heat recovery is stopped there. Thereby, it is possible to suppress the temperature of the cooling water from being raised to the cooling fan operating temperature T _FAN and to prevent the operating rate of the cooling fan 6 from increasing.

  Moreover, since this exhaust heat recovery system can divert devices other than the exhaust heat recovery switching valve 3 such as the radiator 4 and the cooling switching valve 5 as used in the conventional exhaust heat recovery system, Cost increase can be suppressed and the configuration can be simplified.

[4. Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  For example, the method in which the exhaust heat recovery switching valve 3 acquires the temperature information of the cooling water may be constituted by a thermostat instead of the temperature sensor. That is, a thermostat that operates according to the temperature of the cooling water flowing through the first circulation passage 11 is interposed on the first circulation passage 11 so that the exhaust heat recovery switching valve 3 opens and closes according to the operation of the thermostat. It is good also as a structure which is interposed by the exhaust pipe 20 and switches the path | route which exhaust_gas | circulation distribute | circulates.

Further, the cooling switching valve 5 is not limited to a thermostat, and may be constituted by an electromagnetic control valve that is opened and closed by the controller 9 based on a detection value of the temperature sensor 13, for example.
Further, the valve closing temperature T ₁ of the exhaust heat recovery switching valve 3 may not be set lower than the operating temperature T _FAN of the cooling fan 6. In this case, if the temperature of the cooling water reaches T _FAN , the cooling fan 6 operates, but it is possible to secure a longer exhaust heat recovery time accordingly.

1 Engine 2 Waste Heat Recovery Unit 3 Waste Heat Recovery Switching Valve (First Switching Valve)
4 Radiator 5 Cooling switching valve (second switching valve)
6 Cooling fan 7 Oil warmer 8 Water pump 9 Controller (ECU)
DESCRIPTION OF SYMBOLS 10 Flow path 11 1st circulation flow path 12 2nd circulation flow path 12a Cooling flow path 12b Bypass flow path 20 Exhaust pipe 20a Waste heat recovery path 20b Bypass path T ₀ Valve opening temperature (opening temperature) of cooling switching valve
T ₁ closing temperature of the exhaust heat recovery switching valve (first temperature)
T ₂ opening temperature of the exhaust heat recovery switching valve (second temperature)
T _FAN cooling fan operating temperature T _MAX cooling water allowable temperature

Claims (4)

The cooling water flow path of the engine mounted on the vehicle is configured as a parallel flow path branched into a first circulation flow path and a second circulation flow path, and the cooling water of the engine is connected to the first circulation flow path and the second circulation flow path. Flows together with the circulation channel,
The first circulation channel includes an exhaust heat recovery unit that heats the cooling water by exchanging heat between the cooling water and the exhaust of the engine, and a downstream side of the cooling water of the exhaust heat recovery unit an oil warmer for heating the oil by performing the cooling water and the heat exchanger provided is provided,
The second circulation channel is an exhaust heat recovery system provided by further branching into a cooling channel in which a radiator for cooling the cooling water is interposed and a bypass channel that bypasses the cooling channel. ,
First switching for blocking the flow of the exhaust gas into the exhaust heat recovery device according to the state of the exhaust gas flowing into the exhaust heat recovery device and the temperature of the cooling water immediately after passing through the exhaust heat recovery device A valve,
A second switching valve that shuts off the inflow of the cooling water to the radiator when the temperature of the cooling water that has passed through the engine is lower than a predetermined valve opening temperature;
The first switching valve is
When the exhaust flows into the exhaust heat recovery unit and immediately after passing through the exhaust heat recovery unit, the temperature of the cooling water is higher than the valve opening temperature and lower than the allowable temperature of the cooling water. An exhaust heat recovery system that shuts off the inflow of the exhaust gas to the exhaust heat recovery unit when the temperature is equal to or higher than a set first temperature. When the first switching valve shuts off the inflow of the exhaust gas to the exhaust heat recovery device and immediately after passing through the exhaust heat recovery device, the temperature of the cooling water is lower than the second temperature lower than the valve opening temperature. 2, the exhaust heat recovery system according to claim 1, wherein the exhaust gas is caused to flow into the exhaust heat recovery device. A cooling fan for cooling the radiator;
The said 1st temperature is a temperature lower than the cooling fan operating temperature which is the temperature in the said cooling flow path of the said cooling water from which the operation of the said cooling fan is started , The 1st or 2 characterized by the above-mentioned. Waste heat recovery system. An exhaust pipe before Symbol exhaust flows,
The exhaust heat recovery unit and the first switching valve are both interposed on the first circulation channel and the exhaust pipe, and the first switching valve is provided on the downstream side of the cooling water of the exhaust heat recovery unit. And
Before Stories second switching valve, characterized in that it is interposed in front Symbol second circulation channel, the exhaust heat recovery system according to any one of claims 1 to 3.

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